Chester e



UNITED STATES PATENT OFFICE.

CHESTER E. ANDREWS, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE SELDE'A COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF DELAWARE.

DIMETH'YL-DIISOPROPYL-BENZIDIN AND PROCESS OF MAKING SAME.

No Drawing.

To all whom it may concern:

Be it known that I, Cnns'rnn E. ANDREWS, a citizen of the United States, residing at Pittsburgh," in the county of Allegheny and State of Pennsylvania, have invented Dimethyl-Diisopropyl-Benzidin and Processes of Making Same, of which the following is a specification.

The present invention relates to the production of a benzidin derivative, corre-.

- spending to benzidin in a manner analogous to the correspondence between cyme-ne and benzene.

In the operation of the process of my present invention, I preferably start with mono-nitrocymene, which is 1-methyl-2- nitro-4isopropyl-benzene, or, its isomer, 1-methyl-3 nit'ro 4 isopropyl-benzene, and reduce this material in an alkaline liquor, whereby dimethyl-diisopropyl-hydrazo benzene or hydrazo-eymene is produced. The hydrazo-cymene is then subjected to the treatment known as the benzidin transformation whereby the two rings rearrange themselves and. the benzidin derivative is produced.

In a specific example of my process, I first mix 72 parts of nitro-cymene, 20 parts of water and 50 parts'of ethyl alcohol and 250 parts of a 30%solu'tion of caustic soda. These materials are mixed together at ordinary room temperature and are placed in a vessel provided with a reflux condenser, and Zinc dust slowly added, while the mixture is being stirred to make the reaction pro-:

ceed smoothly. During this introduction of zlne dust, the temperature will rise rapidly, but with the refluxeondenser and the agitation, it is not necessary to watch the temperature, it only being necessary to add zine dust at such a rate that the reaction does not become violent.

When the zinc dust has all been added, the reaction mass is stirred for half an. hour or so, without the necessity of controll ng the temperature. By this time the reaction will be substantially complete, and the reaction mixture is diluted with 1,000 parts Specification of Letters Patent.

Patented se t. 2, 1919.

Application filed September 15, 1917. Serial No. 191,605.

will float on the surface, this product consisting essentially of hydrazo-cymene. After settling. the oily layer is drawn off. This material might be purifiedby adding an acid to form a soluble salt of hydrazocymene, for example hydrazo-eymene hydrochlorid, and then steam-distilling to remove other bodies present. This is not necessary under ordinary conditions since it is usually more convenient at a later stage.

To the hydrazo-eymene constituting the oily layer is added 300 to 400 parts of water and the mixture heated to boiling. Hydrochlorie acid is added gradually as long as the acid is absorbed by the liquid. The liquid is then boiled for a short time, 15 or 20 minutes ordinarily being sufiie'ient. The transformation into the benzidin body is now substantially complete. Sulfuric acid is then added to precipitate the sulfate of dimethyl-diisopropyl-benzidin, which is a white crystalline powder. This is then removed from the liquid by filtration, while most of the impurities likely to be present in the original nitro-cymene remain in liquid condition, whereby considerable purification is effected and the sulfate is decomposed by addin for example a solution of caustic soda, which may be from 10 to 15%, preferably not over 15%. This precipitates the dimethyl-diisopropyl-benzidin, which is an 'oil. After settling, the oily layer is drawn on and can be purified by distillation or in any other suitable manner. The dimethyl-diisopropyl-benzidin is an oily liquid boiling at about 250 C.

y The nitro-cymene employed in this treatment may be pure or crude 'and it. is not necessary to previously purify the material. The nitro-cymene may if desired be prepared by nitrating spruce turpentine, for example in accordance with the process of my copending application SerialNo. 191245 filed September 13, 1917, or indirectly by the nitration of 2-acetyl amino cymene and subsequent elimination ofthe acetyl ammo group for example in accordance with the process of my copending application Serial No. 191,60'L filed September 15, 1,917, (synthetic manufacture of thymol) which gives one produced by nitration of spruce turpentine.

The reactions which take place in the process may be conveniently expressed as fol- 5 the mono nitro cymene isomeric with the lows:

. on, on, (211 Reduced inalkaline solution NH-NH- g mom Am n-)2 men), e m

Subjected to benzidin transformation" EgN- "NH3,

. H: v EH03):

a V men wHe, Reducedinalkaliaesolution N -NH N05 -l a H(CH|)| CH: 0'11:

Subject to benzidin transformation Hm NH, a)a U QT I claim: being performed in an alkaline solution to 1. Dimethyl-diisopropyl-benzidin. 2'. Symmetrical dimethyl diisopropylbenzidin, the same being an oily liquid boiling at atemperature of about 250 (3., and the" sulfate of which is an insoluble white crystalline powder.

A process of making dimethyl-diisopropyl-benzidin which comprises reducing crude mono-nitro-cymene as produced by nitrating spruce turpentine, such-.reoluction produce hydrazo-cymene, and subjecting the hydrazo cymene. to the benzidin transformation., whereby dimethyl-diisopropy1- benzidin is. produced, and precipitating a' compound of dimethyl-diisopropyl-benzidin while leaving a large part of the other constituents of'the spruce turpentine in the sorllltiOIl.

- In testimony whereof I aflix my signature.

CHESTER E, ANDREWS. 

